1. Field of the Invention
The present invention pertains to an improved method of supporting a well caisson or drivepipe extension by the use of a submerged support frame which may be installed temporarily and/or permanently, provides for reducing the weight of the caisson and makes the caisson less vulnerable to buckling.
2. Background
In the development of offshore oil and gas wells, one conventional practice involves driving or otherwise installing an elongated caisson or casing member, sometimes also known as a drivepipe, which extends at least from the seafloor to a point above the sea surface so that drilling and various other well operations may be carried out through the caisson or drivepipe. A longstanding problem has been to provide adequate support for such a caisson. In many instances the caisson is required to be particularly heavy walled so that it may be free standing without other support. This, of course, increases the cost of the well and, in many instances, the caisson installation time.
Our U.S. Pat. No. 4,812,080 issued March 14, 1989 and assigned jointly to the assignees of this invention describes a unique support member or "jacket" for supporting an offshore platform wherein two or more piles are provided as the anchoring structure as well as a part of the jacket structure. An arrangement of diagonal and/or lateral braces together with tubular guide sleeves makes up at least one embodiment of the jacket wherein one or more vertical column members are then formed by a well casing and the aforementioned piles.
However, it has been determined that some features of the support member or jacket described in U.S. Pat. No. 4,812,080 may be adapted for use as a totally submerged temporary or permanent support system for a well caisson, drivepipe or similar free-standing well support member. Certain ones of the more important features of the present invention and other superior aspects are described hereinbelow.